In the field of high voltage electronic devices, it is known to implement high voltage (e.g. ˜1500V) isolation between a low voltage (e.g. ˜5V) control integrated circuit (IC) device and a high voltage output driver module. Such isolation is required in order to avoid shorting between the high voltage output and the low voltage control circuitry. FIG. 1 illustrates a simplified block diagram of an example of a high voltage driver application in which high voltage isolation, illustrated generally at 110, is provided between a low voltage control module 120 and a high voltage driver module 130 for driving a high voltage output (not shown).
Typically, such high voltage isolation 110 is implemented using galvanic isolation. Galvanic isolation is a principle of isolating functional sections of electrical systems to prevent current flow; no metallic conduction path is permitted. Energy or information can still be exchanged between the sections by other means, such as capacitance, induction or electromagnetic waves, or by optical, acoustic or mechanical means.
In a conventional capacitance solution, a high voltage capacitor is provided between the low voltage control module 120 and the high voltage driver module 130, for example mounted on a printed circuit board (PCB). A problem with using such a conventional capacitor to provide isolation between the control module 120 and the high voltage driver module 130 is that any short with, say, solder between each terminal of the capacitor could be critical. Another issue is the high voltage capacitor needed to provide the required isolation (e.g. >1500V), which are typically large and expensive.
A typical inductive/electromagnetic galvanic isolation implementation comprises the use of a transformer or similar device which uses electromagnetic fields to convey control signals from the control module 120 to the high voltage driver module 130. Such magnetic devices achieve high voltage isolation by employing opposing inductively coupled coils. However, a problem with such devices is that they typically require high power levels (especially when high data rates are required), and typically require the use of at least three separate integrated circuit devices. As such, such implementations are typically inefficient in terms of both size and power consumption. Furthermore, such magnetic devices are susceptible to electromagnetic interference.
An alternative known galvanic isolation implementation comprises the use of optical devices, which achieve high voltage isolation by employing, for example, light emitting diodes (LEDs) or the like and corresponding photodiodes to transmit and receive control signals as light signals. However, such optical solutions also require high power levels, and suffer from operational and design constraints when multiple communication channels are required.